This document summarizes key aspects of the urinary system including the kidneys, ureters, bladder and urethra. It describes the structures and functions of the nephron, including glomerular filtration, tubular reabsorption and secretion. Hormonal regulation of the urinary system by substances like angiotensin II, aldosterone and ADH is also covered. The document concludes with sections on the composition of urine and age-related changes to the urinary system.

1. Chapter 21
The Urinary System
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2. End of Chapter 21
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3. Urinary System
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Two kidneys and two ureters
Urinary bladder & urethra
Effector organ for
1.
2.
3.
4.
5.
Regulation of Plasma ion composition
Regulation of Body water Volume (BP)
Regulation of blood pH (with lung)
Production of Hormones
Excretion of waste
Copyright 2010, John Wiley & Sons, Inc.

4. Urinary System
Copyright 2010, John Wiley & Sons, Inc.

5. Kidney
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Divided into cortex –outer portion
Medulla- inner portion
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Urine goes into renal pelvis
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Contain renal pyramids & renal columns
Edges are made of major & minor calyces
Then out ureter
Copyright 2010, John Wiley & Sons, Inc.

6. Kidney
Copyright 2010, John Wiley & Sons, Inc.

7. Renal Blood Supply
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20-25% resting CO goes through kidneys
 L. & R. renal arteries then
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Segmental  interlobar  arcuate  interlobular
 afferent arterioles
 glomerulus (capillary network)
 efferent arterioles
 peritubular capillaries  veins
   renal vein
Capillaris Units –nephrons grouped at pyramids
Copyright 2010, John Wiley & Sons, Inc.

8. Renal
Blood
Supply
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9. Renal Blood Supply
Copyright 2010, John Wiley & Sons, Inc.

10. Nephron
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Unit of renal function: corpuscle & tubule
Corpuscle: forms filtrate
Glomerulus & Glomerular capsule (cortex)
Proximal convoluted tubule (cortex) 
Descending Loop of Henle (into medulla)
ascending Loop of Henle (into medulla) 
Distal convoluted tubule (cortex) 
Collecting duct minor calyx
Copyright 2010, John Wiley & Sons, Inc.

11. Nephron
Copyright 2010, John Wiley & Sons, Inc.

12. Basic Operation
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Glomerular filtration-filter plasma
Tubular reabsorption
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Tubular Secretion
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Reabsorb needed compounds & water from
filtrate
Secrete some materials into filtrate
Let rest go out as a solution called urine–see
Table 21.1
Copyright 2010, John Wiley & Sons, Inc.

13. Basic Operation
Copyright 2010, John Wiley & Sons, Inc.

14. Glomerular Filtration
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Two layers of capsule surround glomerulus
Between is capsular space
Podocytes support capillary epithelium
Form filtration membrane
Permeable to water & solute
but not most proteins & blood cells
Copyright 2010, John Wiley & Sons, Inc.

15. Filtration Pressure
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Blood pressure for filtration
Opposed by colloid osmotic pressure and
capsular pressure
Efferent and afferent arteriole diameters
adjust to maintain a net filtration pressure

Even with small changes in blood pressure
Copyright 2010, John Wiley & Sons, Inc.

16. Glomerular Filtration Rate
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= GFR 105-125 ml/min
Determines net reabsorption because it
determines filtrate flow
ANP increases GFR
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Responds to increased blood volume
Sympathetic stimulation  vasoconstriction
 decreased GFR
 Urine production
Copyright 2010, John Wiley & Sons, Inc.

17. Glomerular Filtration
Copyright 2010, John Wiley & Sons, Inc.

18. Tubular Reabsorption
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Proximal tubule
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~65% Na+ & H2O
Normally 100% nutrients
~100% HCO3- (depends on blood pH)
Active transport of solutes
Osmosis moves water
Cells distal to proximal tubule fine tune
reabsorption under control
Copyright 2010, John Wiley & Sons, Inc.

19. Tubular Secretion
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Takes place all along tubule
Major substances : H+, K+, ammonia, urea,
creatine, drugs like penicillin
Helps regulate plasma pH 7.35-7.45
Diet is acid  urine is typically acidic
Copyright 2010, John Wiley & Sons, Inc.

20. Urine Route
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Collecting ducts to calyces
Calyces to ureter
Ureter to bladder
Bladder to urethra
Copyright 2010, John Wiley & Sons, Inc.

21. Filtration, Reabsorption,
Secretion
Copyright 2010, John Wiley & Sons, Inc.

22. Hormonal Regulation
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Angiotensin II & aldosterone
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Angiotensin II- stimulates NaCl in proximal tube
Aldosterone- increases Na+ reabsorption & K+
secretion in DCT & CD
More ions reabsorbed more water
ANP-increases GFR & inhibits aldosterone
action less Na+ reabsorbed
ADH- responds to increased concentration of
solute in blood + fall in BP
Copyright 2010, John Wiley & Sons, Inc.

23. Hormonal Regulation
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ADH: important to body water balance
Increased concentration of solute in blood +
fall in BP ↑ ADH
With no ADH: DCT & CD walls are
impermeable to water dilute urine
With ADH: water reabsorption occurs
concentrated urine
Copyright 2010, John Wiley & Sons, Inc.

24. Components of Urine
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Urine = 1-2 l /day
95% water
+ urea, creatine, K+, ammonia, uric acid, Na+,
Cl-, Mg2+, sulfate, phosphate & Ca2+
Depends on diet and state of health

See table 21.3
Copyright 2010, John Wiley & Sons, Inc.

25. Regulation of
Water
Reabsorption
Copyright 2010, John Wiley & Sons, Inc.

26. Urine Route
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Collecting ducts calyces
Ureter
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Bladder- directly in front of rectum
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Lined with mucus & transitional epithelium
Pass under bladder
Full bladder prevents backflow
Can stretch (700-800 ml)
Smaller in females because of uterus
Three layers of detrussor muscle
 Urethra- internal urethral sphincter
External urethral sphincter (voluntary)
Copyright 2010, John Wiley & Sons, Inc.

27. Urine Route
Copyright 2010, John Wiley & Sons, Inc.

28. Micturition = Urination
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Autonomic reflex- internal sphincter
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Responds to stretch like rectum
Parasympathetic  detrusor muscle
contraction
Conscious control-external sphincter
Copyright 2010, John Wiley & Sons, Inc.

29. Aging
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Kidneys shrink- decrease in capacity
Thirst decreases  dehydration
 urinary tract infections
Males: prostate enlargement frequent
urination & slow flow
Females: more prone to leakage of external
sphincter (incontinence)
Both: nocturia
Copyright 2010, John Wiley & Sons, Inc.